The present invention is directed to a toric pump incorporating an improved housing construction enabling a drive motor, pump and filter to be readily mass produced and assembled into a single compact package.
Although useful in other applications, the pump disclosed in the present application is especially designed to supply air to the exhaust emission control system of an automotive vehicle. As such, because of the large number of pumps required, part fabrication and assembly costs must be kept at a minimum. A toric pump such as that disclosed in the aforementioned parent application Ser. No. 07/502,157 is well adapted to produce the required air flow for the emission control system application by means of a pump of extremely compact size. The present invention is directed to structural features of such a pump which minimize part fabrication and assembly costs.
In a toric pump such as that disclosed in parent application Ser. No. 07/502,157, one critical dimension of the assembled pump is the axial clearance between the opposed side surfaces of the impeller and the adjacent wall surfaces of the pump housing and a second critical dimension is the radial clearance between the periphery of the impeller and the stripper portion of the impeller receiving chamber which separates the outlet end of the pump chamber from the inlet end. Clearance between the impeller and chamber walls at the stripper portion must be extremely close to minimize leakage from the high pressure region at the outlet end of the pump chamber to the relatively low pressure region at the inlet end of the pump chamber.
The present invention enables a precise establishment of housing to impeller clearance to be achieved by machining of a single part. The present invention also is designed for simple and efficient assembly.